This invention relates to frequency synthesizers and, more particularly, to those in the microwave frequency range which are stable, have low noise and are rapidly switchable between specific frequencies.
Present radar detection equipment has become very sophisticated and has created for need for lower power/spectral profile radar transmissions in order to avoid detection. A method to attain a lower power/spectral profile is the use of high duty factor, low peak power waveforms. Although high duty factor radar waveforms have been extensively used in airborne and space applications, ground-based radars have traditionally used low duty factor, high peak power waveforms. A major reason for this in ground radar installations is that the requirement for short range ground clutter rejection imposes stringent stability requirements on the radar exciter.
A method which makes the radar system less visible to detection equipment is the use of frequency agility. Changing frequencies between successive radar beams would require detection equipment to perform instantaneous frequency measurement and complex signal sorting, especially if multiple radars are operating in the same vicinity. This presents a large burden to the detection equipment.
In order to produce a radar system which can function in a ground installation and use high duty factor, low peak power waveforms, a low noise frequency synthesizer in the radar exciter is required. To produce frequency agility, this frequency synthesizer must have multiple output frequencies which may be rapidly changed.
It is therefore a purpose of the invention to provide a frequency synthesizer having a lower power/spectral profile signal in order to be less visible to radar detection equipment.
It is also a purpose of the invention to provide an ultra low noise and highly stable frequency synthesizer.
It is also a purpose of the invention to provide a low noise microwave frequency synthesizer such that it can be operated in a high duty factor mode in a ground installation application.
It is also a purpose of the invention to provide an improved frequency synthesizer which can rapidly change output frequencies.